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Clinohumite

Discovered in 1876; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

(Mg,Fe++)₉(SiO₄)₄(F,OH)₂

Manganese Iron Silicate Fluoride Hydroxide

Molecular Weight:

695.05 gm

Composition:

Magnesium

23.60 %

Mg

39.14 %

MgO

Iron

18.08 %

Fe

23.26 %

FeO

Silicon

16.16 %

Si

34.58 %

SiO₂

Hydrogen

0.07 %

H

0.65 %

H₂O

Oxygen

37.98 %

O

Fluorine

4.10 %

F

4.10 %

F

—

— %

O

-1.73 %

-0=F₂

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/B.04-40

8 : Silicates
B : Nesosubsilicates, with anions unfamiliar to tetraheders, cations of octahedral and tetrahedral orientation [4/6]
04 : Humite group

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Crystals are complex, highly modified, to 2 cm; massive. Twinning: Common, simple, lamellar.

Physical Properties

Cleavage:

[100] Poor

Fracture:

Uneven to Sub-conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.0

Density:

3.17 - 3.35 (g/cm³)

Radioactivity:

Not Radioactive

Optical Properties

Color:

White, Yellow, Orange, Reddish orange, Reddish brown, Brown

Transparency:

Transparent to Translucent

Luster:

Vitreous

Refractive Index:

1.628 - 1.674  Biaxial ( + )

Birefringence:

0.0260 - 0.0280

Dispersion:

Strong

Pleochroism:

X = golden yellow, yellow-brown, deep reddish yellow; Y = pale yellow, yellow-orange, light yellow; Z = pale yellow, yellow-orange, colorless.

Occurances

Geological Setting:

In contact metamorphic zones in dolostones and metasomatized limestones adjacent to felsic plutonic rocks; in serpentine and talc schists; in a carbonatite.

Type Locality:

Monte Somma, Somma-Vesuvius Complex, Naples Province, Campania, Italy

Year Discovered:

1876

View mineral photos:

Clinohumite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Clinohumite is a member of the Humite Group of minerals that includes Chondrodite, Clinohumite, Humite and Norbergite. It is a very beautiful and rare gem and is usually very small and included. The best Clinohumite has an intense and bright orange color with few inclusions. Clinohumite colors include white, yellow, orange, reddish orange, reddish brown and brown. Its strong dispersion and bright colors make for very attractive gems.

Clinohumite was discovered in 1876 as indistinct grains embedded in limestone on Mount Vesuvius near Naples, Italy. In 1983, the first deposit of gem quality crystals was discovered near Lake Baikal, in the Pamir Mountains, Tajikistan (former USSR). It was the only such deposit known until the discovery of gem quality material in the Taymyr region of northern Siberia in 2000 and a recent find in Mahenge, Morogoro Region, Tanzania, Africa in 2005. The best color and quality Clinohumite is still from the find in the Pamir Mountains. Gems from Mahenge, Tanzania and Taymyr Region, Siberia are reported to be a dark, reddish brown while the Pamir gems are a bright yellow to orange or brownish orange. The native people of the Pamir Mountains call the region "Pomir" which means "the roof of the world." This is because of the incredible heights of their mountains. The highest mountain, at 24,590 ft (7,495 m), is Ismail Samani Peak (known as Stalin Peak from 1932-1962 and Communism Peak from 1962-1998).

Clinohumite was named in 1876 by French mineralogist Alfred Lewis Oliver Legrand Des Cloizeaux (1817-1897) in referrence to its monoclinic crystal structure and relationship to Humite, which was named after Sir Abraham Hume (1749-1838), English connoisseur and collector of gems, minerals, and artwork.

There are other locations for Clinohumite, including Tilly Foster Mine, New York; Fort Defiance, Apache County, Arizona; Fresno County, California; Luna, New Mexico and Franklin, New Jersey, USA, but these locations do not produce gem quality material.

Clinohumite gems for sale: